Exposure evaluation is a crucial step for quantitative risk assessment of methomyl.

Methomyl, methyl N-[[(methylamino)carbonyl]oxy]ethanimidothioate is a carbamate insecticide with anticholinesterase activity. As a broad spectrum insecticide, it is one of the most frequently used pesticides in tangerine orchards in Thailand. Although methomyl is said to be rapidly eliminated from experimental animals (1) high incidence of acute poisonings was reported among patients occupationally exposed to a powder formulation of methomyl (2, 3). In this passive dosimetry study of tangerine growers, during mixing and overhead spraying of a 90% powder formulation of methomyl, ocular and nasal exposure was measured. Exposure data are discussed in terms of the "potentially absorbed" or "internal dose".